1. Field of the Invention
This invention relates to a large screen display apparatus made up of a number of light emitting elements which is installed mainly at outdoor stadiums or the like.
2. Description of the Prior Art
In general, in a large screen display apparatus of this type, a display section :s made up of a number of signal picture element light emitting elements which are CRTs or light bulbs. In a color display apparatus, three kinds of single picture element light emitting elements; i.e., red (R), green (G) and blue (B) single picture elements are arranged regularly, or a number or single picture element light emitting elements including three colors, red, green and blue, are arranged in matrix form. More specifically, the display apparatus comprises a number of units including a plurality of light emitting elements and an electronic circuit for driving them, and is provided with a control device for controlling the display operation and a power source.
FIG. 1 shows one example of such a conventional display apparatus. In FIG. 1, reference numeral 30 designates a screen of the display apparatus; 3, units forming the screen 30; 6, a housing which accommodates a plurality of units 3, thus forming the screen; 13, a power source; and 29, a display control section for controlling the units 3 of the screen 30.
FIG. 2 is a block diagram showing the arrangement of the display control section 29. In FIG. 2, reference numeral 26 designates an analog-to-digital converter for converting an input video signal into a digital signal (hereinafter referred to an "an A/D converter", when applicable); 15, a frame memory for storing video signals digitized; 16, an on-off decision section connected to the frame memory 15; 27, a column selecting circuit connected to the on-off decision section, for selecting a column in the screen 30; 28, a line selecting circuit for selecting a line in the screen 30; 18, an address control section for performing the address control of the line selecting circuit and the frame memory 15; 22, a timing control section for performing the timing control of the A/D converter 26; and 32, single picture element light emitting elements forming the above-described units 3.
The operation of the display apparatus thus constructed will be described. A video signal applied to the display apparatus is converted into a predetermined digital signal by the A/D converter 26, which is stored in the frame memory 15. The data stored in the frame memory 15 are read out according to addresses corresponding to the single picture element light emitting elements so as to be converted into on-off signals successively, which are supplied to the light emitting elements 32 which are specified by the column selecting circuit 27 and the line selecting circuit 28. Each single picture element light emitting element 32 has a function of storage, and the on-off signal supplied to the single picture element light emitting element 32 is held thereby until another signal is supplied thereto. With respect to the contents of the frame memory 15, the data of each field are read out a plurality of times and converted into predetermined on-off signals so as to be displayed, and the accumulation of "on" time in one field is proportional to the amplitude of a video signal to be displayed by the single picture element light emitting elements 32.
A variety of screens 30 different in size can be provided by changing the arrangement of the units 3. The control device 29 can control the variety of screens.
The conventional display apparatus is designed as described above. Therefore, the resolution cannot be increased without increasing the density in arrangement of single picture element light emitting elements which are smaller in size. Accordingly, the number of single picture element light emitting elements used is extremely large, and at the same time the numbers of drive circuits and other peripheral circuits are unavoidably large. The manufacturing cost may be reduced by miniaturizing the single picture element light emitting elements; however, the amount of reduction is considerably small. And in this case, the drive circuits and the peripheral circuits should be miniaturized. Therefore, it is considerably difficult to increase the resolution, and to decrease the manufacturing cost, the weight and the width of the display apparatus at the same time.
Conversion of digital data stored in memory into those having predetermined time widths is one of the most important signal processing operations in the display apparatus. If the signal processing sections, which are heretofore located at a position, are assigned to the modules, respectively, then the manufacturing cost of the display apparatus is increased.